Coating machinery



June 1965 P. A. PETERSON ETAL 3,187,716

COATING MACHINERY 2 Sheets-Sheet 1 Filed Sept. 19, 1962 I June 1965 P. A. PETERSON ETAL 3,

COATING MACHINERY 2 Sheets-Sheet 2 Filed Sept. 19, 1962 United States Patent 3,187,716 COATING MACHINERY Philip A. Peterson, Worcester, and Nicolas M. Reitzel, Boylstou, Mass., assignors to Rice Barton Corporation, Worcester, Mass, a corporation of Massachusetts Filed Sept. 19, 1%2, Ser. No. 224,652 3 Claims. (Cl. 11863) The present invention relates to improvements in coating processes and machinery, particularly in a process and in coating machinery for carrying out such a process in which a surplus of coating is applied to a moving web,

the excess being removed and the retained coating being smoothed by a metering device following the application of said excess coating.

It is a principal object of the invention to provide an improved process and associated apparatus for coating a traveling web, which is well adapted for applying the coating evenly and with the desired thickness independently of variations of tension applied to the feeding web and independently of the speed of the feeding web.

It is a further object of the invention to provide an apparatus for applying a coating to a traveling web in which the time elapsed between the initial application of the coating and the removal of excess material, as for example by means of an air knife or other metering device, is very short indeed permitting the use of coatings containing higher solids than would otherwise be possible.

It is a further object of the invention to provide a simplified and more compact apparatus for coating a traveling web which will be easier and cheaper to install, and more reliable in operation.

A feature of the invention consists in the provision of means for feeding a web downwardly between a backing roll and a coating roller, supplying a coating material to the web in such a manner that a pool is formed at the ingoing nip between the web and coating roller while at the same time an adjustment of said rollers is maintained such as to insure a proper application of the coating material, and immediately thereafter as the coated web emerges from the outgoing nip removing the excess coating and smoothing the coating retained by the web before the coating material will have had the opportunity to dry out or to set.

With the above and other objects in view as may hereinafter appear the several features of the invention will be readily understood by one skilled in the art from the following description taken in connection with the accompanying drawings, in which:

FIG. 1 is a sectional plan view of a specific embodiment of the invention in which an air knife is employed as the metering device following application, taken on a line 1-1 of FIG. 2 and embodying therein the several features of the invention;

FIG. 2 is a sectional view in side elevation of the air knife coater device on a line 22 of FIG. 1; and

FIG. 3 is a sectional view of a modified form of the coating device using a trailing blade as a .following metering device.

In coating devices of the nature described, in past use, the process of coating Webs, and more particularly, paper of various types including board, consists normally of feeding the web to the coating device at a tension which is determined by the character ofthe web material and at a speed determined by various machine factors. Coating is applied to the web in such machines by an applicator roll or rolls running at a differential or reverse speed and dipping into a pan of coating. An excess of coating is applied to the web which is subsequently stripped off, and the remainder smoothed out by means of an air knife or other metering devices. Coat weight applied before I would apply coating to the uncoated side of the web, edge the stripping by the following metering device is controlled by the differential speed of the applicator roll and the web and by the wrap of the web on the applicator roll and by the composition of the coating material. carrying out the method above referred to, it has been found that the thickness and uniformity of the coating applied is greatly affected by the level of tension main-' tained on the web and by the speed of the web. In the coating of board, where heavy tension is mandatory, difliculty has been encountered in obtaining a sufficiently uniform, evenly spread coating, free of patterning, for the following metering device to produce a satisfactory coating. Similarly, at very high web speeds, difiiculty is found in preventing centrifugal throwoff of coating from a small diameter applicator roll, and patterning from film splitting is accentuated at higher speeds. V

In carrying out the present invention an applicator assembly is provided which permits a ready adjustment of the thickness of the coating applied and a uniform application of said coating which is wholly independent of the tension applied against the web. Further, the'unit may be operated at substantially higher web speeds than present methods allow. As shown in the drawings, a web 18 is fed vertically downwardly from a guide roll 28 around a backing roll 22, and thence upwardly to the coating drying section or other subsequent finishing operation. The guide roll and backing roll may be turned by the web or alternatively may be driven at web speed from an outside source diagrammatically shown in FIG. 1 as an electric motor 23 connected by a belt24 with one end of the supporting shaft 30 for the backing roll 22. The web during its downward traverse is engaged also by a coating roll 26 which is externally driven independently of web speed by a drive which may comprise an electric motor 27 and a connecting belt 29 capable of producing rotation in either direction at any desired speed relative to the speed of the web, and which turns on an axis 28 parallel to the axis 3t! of the backing roll 22,

said axes being located in a plane sufiiciently close to the horizontal to maintain a coating puddle at the ingoing nip. As shown the coating roll 26 is arranged for transverse adjustment in said plane toward and away from' formed between. the web and the coating roll 26. Flow of coating material in said pool'is regulated by valves 37 in each branch pipe. The thickness anduniformity of the coating applied is determined by, the adjustment of the coating roll 26 toward or away from the backing roll 22 and web carried thereon, and by the rate and direction of rotation imparted to the coating roll 26. The excess coating material is collected ina pan 38A located beneath the coating roll 26. The collected material is drawn off through a pipe 40, and-is returned to coating supply not shown for recirculation through the manifold 34. In order to avoid soiling the end surfaces of the backing roll and the accumulation of coating on the backing roll that doctors 46 are installed in position to remove coating material from the end surfaces of said backing roll, maintaining those end surfaces in a clean condition. The edge doctors are so angled as to permit the continuous removal and return of coating material collected to the color sup 'rnately of rotation on the baclc'ng roll 22, the coat- Patented June 8, 1965 3 ing is subjectedto-the action of an air knife 44 which may beof a conventional type and which acts to blow off the excess coating and to smooth the remainder to form an evenly distributed film of uniform thickness. The backing roll is-further cleaned by means of the edge doctors 46 above referred to located to engage against a portion of the backing roll located slightly beyond the highest point of rotation. A doctor blade 47 or shower 48 or both may be installed on coating roll 26 to main 'tain this roll in clean condition. Installation of these equipages in a conventional air knife coater is diflicult by the doctor blade 49 as a flexible doctor metering devices A typical operation of the apparatus illustrated in accordance with the invention follows:

A- dry coating weight of 16.7 pounds per 3000 square feet of web is applied at a web speed of 250 feet per minute, using a doctoring air pressure of 1.25 pounds per square inch. The coating consists of a clay-adhesive mixture of 45 percent solids content and a viscosity of 700 centipoises as measured at 60 revolutions per minute with a .Brookfield viscosimeter with No. l spindle. In

this operation the applicator roll is operated at 150 feet per minute surface speed in the direction of travel of the Web and with a gap of 0.006 inch between web and applicator roll. The resulting coating is of satisfactory quality and uniformity.

It will be understood that substantial variations may be made in web speed, sheet tension, coat weight, and coating properties with similarly satisfactory results over wide ranges by appropriate adjustment of air knife pressure, applicator roll speed and nip opening;

The construction shown has important advantages in that the coating application is entirely independent of sheet tension which, as previously pointed out, may vary over very wide limits depending on the character of the web material subjected to the coating operation. Operating speed may further be substantially increased because of reduced applicator roll speed and consequent reduction of centrifugal flinging of coating. A further advantage consists in the very short time which elapses between the coating application and the subsequent metering and smoothing of same so that the coating will not have had any opportunity to harden. The mobility of the coating as it passes the metering device is, therefore, substantially higher thus permitting higher solids to be used where so desired. A further advantage consists in the extremely simple and compact construction which has been evolved iwhich has been found substantially cheaper to manufacture, and to present fewer problems of installation than web coating applicators previously known in the prior art.

A further advantage is the substantially reduced horsepower requirement for the coating roll drive. Since the web under tension does not wrap on the coating roll, traveling at differential speed, frictional forces from the web wrapped on coating roll and opposing rotation of same are absent.

The various embodiments described are but a few pos sible applications of the invention and specific structures may be substituted for those described without altering the essence of the invention as claimed. In particular, it is apparent that any type of metering device, requiring the application ofan excess of coating material, may be substituted for the devices shown without altering the essence of the invention.

The invention having been described what is claimed is:

1. A coating applicator assembly which comprises, in combination, rollsfor supporting a traveling web including a backing roll through which the web is fed in a downward direction and about which the Web is wrapped through a substantial angle and drawn olf in an upward direction, a coatingfiroll supported in parallel relation to and closely adjacent said backing roll at the side thereof providing a downward incoming nip to receive said web, and adapted to maintain a pool of coating material between the web and the coating roll, means for supporting said rolls in an adjusted spaced relation to one another suitable for applying said coating material to the web passing therebetween, means for supplying an excess of coating material into said pool, a doctoring device acting against a portion of said coated web wrapped around said backing roll and spaced from said incoming nip upon an upwardly moving portion of said backing roll for removing excess coating material and for smoothing the coating material on said web, and means to draw off said excess of coating material.

2. A coating applicator assembly according to claim 1 in which said doctoring device comprises an air knife acting against said portion of said web wrapped about said backing roll.

3. A coating applicator assembly according to claim 1 in which said doctoring device comprises a flexible doctor blade and means for supporting said doctor blade against a portion of said web wrapped about said backing roll.

References Cited by the Examiner.

UNITED STATES PATENTS 1,838,358 12/31 Bradne-r 117lll X 1,901,080 3/33 Bradner 117111 X 1,944,835 1/34 Boyers 1l711l X 2,257,373 9/41 FanselOW 11 7-102 2,534,320 12/50 Taylor 117ll1 X 2,679,231 5/54 Pomper et a1. 11863 2,729,192 1/ 5 6 Warner 118-405 2,953,476 9/60 Armstrong 117-111 3,029,780 4/62 Justus et a1 118-126 RICHARD D. NEVIUS, Primary Examiner.

JOSEPH B. SPENCER, Examiner. 

1. COATING APPLICATOR ASSEMBLY WHICH COMPRISES, IN COMBINATION, ROLLS FOR SUPPORTING A TRAVELING WEB INCLUDING A BACKING ROLL THROUGH WHICH THE WEB IS FED IN A DOWNWARD DIRECTION AND ABOUT WHICH THE WEB IS WRAPPED THROUGH A SUBSTANTIAL ANGLE AND DAWN OFF IN AN UPWARD DIRECTION, A COATING ROLL SUPPORTED IN PARALLEL RELATION TO AND CLOSELY ADJACENT SAID BACKING ROLL AT THE SIDE THEREOF PROVIDING A DOWNWARD INCOMING NIP TO RECEIVE SAID WEB, AND ADAPTED TO MAINTAIN A POOL OF COATING MATERIAL BETWEEN THE WEB AND THE COATING ROLL, MEANS FOR SUPPORTING SAID ROLLS IN AN ADJUSTED SPACED RELATION TO ONE ANOTHER SUITABLE FOR APPLYING SAID COATING MATERIAL TO THE WEB PASSING THEREBETWEEN, MEANS FOR SUPPLYING AN EXCESS OF COATING MATERIAL INTO SAID POOL, A DOCTORING DEVICE ACTING AGAINST A PORTION OF SAID COATED WEB WRAPPED AROUND SAID BACKING ROLL AND SPACED FROM SAID INCOMING NIP UPON AN UPWARDLY MOVING PORTION OF SAID BACKING ROLL FOR REMOVING EXCESS COATING MATERIAL AND FOR SMOOTHING THE COATING MATERIAL ON SAID WEB, AND MEANS TO DRAW OFF SAID EXCESS OF COATING MATERIAL. 